1. Field of the Invention
The present invention relates to an apparatus and a method of calculating a wheel speed by using a tire force sensor and a chassis control system using the same, and more particularly, to an apparatus and a method of calculating a wheel speed of a vehicle and a chassis control system using the same, in which the wheel speed is calculated by using a characteristic that a signal outputted from a tire force sensor has a peak value in a predetermined cycle.
2. Description of the Related Art
A chassis control system that controls the stability of a vehicle typically includes an anti-lock brake system (ABS), a traction control system (TCS) and an electronic stability control (ESC).
The TCS is an electronically controlled driving apparatus that is used to maximize acceleration of the vehicle by appropriately controlling slip of one or more wheels when the vehicle starts traveling or accelerates, and is used to reduce an engine torque when the vehicle travels around a curve to prevent the vehicle from “rolling over”. More specifically, TCS is typically (but not necessarily) a secondary function of the ABS. TCS is typically designed to prevent the loss of traction of the driven road wheels, and therefore maintains the control of the vehicle when excessive throttling is applied by the driver and the condition of the road surface (due to varying factors) is unable to cope with the torque applied.
The ESC is a computerized technology that improves safety of a vehicle's stability by detecting and minimizing skids. When ESC detects loss of steering control, it automatically applies the brakes to help “steer” the vehicle where the driver intends to go. Braking is automatically applied to wheels individually, such as the outer front wheel to counter oversteer or the inner rear wheel to counter understeer. Some ESC systems also reduce engine power until control is regained. ESC does not improve a vehicle's cornering performance; instead, it helps to minimize the loss of control.
Generally, the chassis control system controls the vehicle at appropriate times when a driver cannot maneuver the vehicle alone, thereby ensures the stable operation of the vehicle. To this end, the conventional chassis control system controls the safety of the vehicle based on the wheel speed sensor mounted on the left, right, front and rear wheels.
FIG. 1 illustrates a conventional wheel speed sensor. As shown in FIG. 1, the conventional wheel speed sensor includes a tone wheel unit 11, which rotates with the wheel, and a hall sensor 12, which detects rotation. The tone wheel unit 11 of the conventional wheel speed sensor is exposed to the outside elements (see FIG. 2), and therefore, the tone wheel unit 11 may easily be damaged by, for example, gravel, dirt, etc., and accordingly when the tone wheel unit 11 is exposed to the elements for a long time, the recognition rate of the wheel speed sensor can be lowered due to foreign material introduced thereto. Furthermore, the chassis control system which relies on the wheel speed sensor for its data, can only detect when the wheel speed sensor becomes defective. It cannot however tell when foreign elements have been introduced into the tone wheel unit 11.
Thus, in the conventional chassis control system, when a wheel speed is not obtainable or is incorrect due to a defect in the wheel speed sensor, it is difficult to properly control the operational safety of the vehicle and thus a more effective system is required.